Peritoneal Cancer Index Dominates Prognosis After CRS-HIPEC for Colorectal Peritoneal Metastases: A Consecutive Single-Centre Cohort with 3-Year Follow-Up.

BACKGROUND: Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) can cure selected patients with colorectal peritoneal metastases (CPM). Real-world prognostic data, especially for the Peritoneal Cancer Index (PCI) and completeness of cytoreduction (CCR), are limited. METHODS: We retrospectively analysed 75 consecutive patients treated with CRS + HIPEC at a tertiary centre (2014-2022), giving ≥36 months potential follow-up. Overall survival (OS) was assessed by Kaplan-Meier and Cox models. PCI was grouped 0-10, 11-20, >20; CCR was dichotomised (CCR-0 vs. CCR 1/2). Multivariable analysis included PCI, CCR, and resection extent; HIPEC drug was examined univariately. RESULTS: The median follow-up was 41 months. Crude 3-year OS was 50.7% (38/75). Survival decreased with higher PCI: 69% for 0-10 (n = 42), 38% for 11-20 (n = 21), and 0% for > 20 (n = 4). Versus PCI 0-10, the adjusted hazard ratios (HR) were 3.02 (95% CI 1.52-6.03) for PCI 11-20 and 7.29 (1.72-30.81) for > 20. CCR-0 improved OS univariately (HR 0.43) but was non-significant after adjustment (HR 0.89). Resection limited to the peritoneum (HR 0.99) and choice of intraperitoneal drug showed no independent effect. CONCLUSIONS: In this real-world cohort, PCI was the only independent predictor of 3-year survival after CRS + HIPEC for CPM; neither CCR status, surgical extent, nor HIPEC agent altered prognosis once PCI was considered. PCI should therefore remain the principal selection criterion while molecular and biological markers are integrated into future risk models.